Breadcrumb Navigation

Tornado

Tornado

A tornado is a violent atmospheric wind storm that extends from a thunderstorm to the ground in a funnel shape. Very often tornadoes form out of supercell thunderstorms, which are storms that last for a number of hours, have a rotating updraft of wind and have a hook or pendant shape on radar.

The updraft of wind in these weather systems contributes to the formation of a tornado. Wind that is closer to the ground moves at a slower speed in one direction and gets caught in a storm’s updraft that is moving faster and in the opposite direction. This is called a wind shear. The updraft tilts the wind closer to the ground to a vertical angle resulting in a column of rotating air that forms tornadoes.

Read more about 'Tornadoes'

Visible clues of a tornado can be difficult to spot as some tornadoes never form a visible funnel. But dark green skies, walls of clouds with large hail and a loud roar similar to a freight train are good indicators that conditions are ripe for a tornado.

In the event of a tornado, it’s best to move to either a basement or the lowest possible floor in a building. If a basement is not available, an interior room of the building that is away from windows, such as a hallway or bathroom, is the second best option.

Tornado videos can be as powerful as tornadoes themselves, so MNN rounded up some of the wildest funnels ever caught on film. Here's our top 10 tornado video countdown -- and we saved the best for last.